Multispeckle autocorrelation spectroscopy and its application to the investigation of ultraslow dynamical processes

We describe a modification of conventional dynamic light scattering (DLS) using a CCD camera as optical area detector. Scattered intensity autocorrelation functions are determined using both ensemble- and time-averaging. Therefore, the new setup allows for much shorter measurement times compared to conventional DLS. Our apparatus has been checked by investigating a dilute dispersion of polystyrene (PS)–microgel lattices in glycerol. The results agree well with DLS measurements using the standard setup. Further, we present data for ultraslow dynamical processes in highly concentrated nonergodic suspensions of PS–microgel lattices, where the new technique, due to its shorter measurement time and much better statistical accuracy as compared to conventional DLS, is most useful.